Golf balls can generally be divided into two classes: solid and wound. Solid golf balls include one-piece, two-piece (i.e., solid core and a cover), and multi-layer (i.e., solid core of one or more layers and/or a cover of one or more layers) golf balls. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by tensioned elastomeric material, and a cover. Solid balls have traditionally been considered longer and more durable than wound balls, but also lack the particular “feel” that is provided by the wound construction and typically preferred by accomplished golfers.
By altering ball construction and composition, manufacturers can vary a wide range of playing characteristics, such as resilience, durability, spin, and “feel,” each of which can be optimized for various playing abilities. One golf ball component, in particular, that many manufacturers are continually looking to improve is the center or core. The core becomes the “engine” of the golf ball when hit with a club head. Generally, golf ball cores and/or centers are constructed with a polybutadiene-based polymer composition. Compositions of this type are constantly being altered in an effort to provide a targeted or desired coefficient of restitution (“COR”) while at the same time resulting in a lower compression which, in turn, can lower the golf ball spin rate, provide better “feel,” or both. This is a difficult task, however, given the physical limitations of currently-available polymers. As such, there remains a need for novel and improved golf ball core compositions.
Manufacturers also address the properties and construction of golf ball intermediate and cover layers. These layers have conventionally been formed of ionomer materials and ionomer blends of varying hardness and flexural moduli. This hardness range is still limited and even the softest blends suffer from a “plastic” feel according to some golfers. Recently, however, polyurethane-based materials have been employed in golf ball layers and, in particular, outer cover layers, due to its softer “feel” characteristics.
There remains a need, however, for improved polyurethane blends having further reduced or modified hardness and modulus while maintaining acceptable resilience and superior abrasion resistance and feel. The present invention provides such materials. Golf balls having components formed of plasticized polyurethanes (“PPU”) or blends thereof have preferred characteristics of good resilience, durability, and “feel,” while potentially providing a way for manufacturers to reduce costs compared to other materials having similar properties. Plasticizers are generally used in plastics (i.e., PVC) to adjust the hardness, flexibility, and processing characteristics. Plasticizers are also used in some commercial polyurethane elastomer formulations to provide products exhibiting higher flexibility, lower hardness, and lower rebound resulting in increased energy absorption. Therefore, the addition of PPU's to golf ball composition will allow for a wide range of physical properties, ranging from a very soft gel or gel-like material to a semi-rigid material, depending on the chemistry of the polyurethane and the amount of plasticizer used.